The invention relates to a device for the inspection of surfaces as disclosed in the introductory part of claim 1, as well as to a mode filter as disclosed in the introductory part of claim 7, and to a method for the inspection of surfaces as disclosed in the introductory part of claim 9.
WO 97/34123 teaches the use of a laser for the inspection of surfaces where the light reflected by the surface is detected. When a defect occurs in or on the surface, the light applied to the surface by the laser light source is reflected in such a manner that at least a part of the light is scattered by the defect. The intensity thus decreases in the reflected component. Therefore, localization of defects is possible by measurement of the intensity of the reflected light. The resolution is limited and amounts to approximately 500 nm. Such a resolution, however, is not fine enough for the microstructures with conductor tracks or component groups that are situated very close to one another. Even when the scattered light that occurs at the defect is detected, the best sensitivity that can be achieved lies in the range of approximately 60 nm. In order to enhance the sensitivity, it would be necessary to reduce the irradiated region. However, the measurement would then become very time consuming.